Saturday, October 28, 2017

How to Perform DTD Comparison on Two SGML Or XML DTD Files

How to Perform DTD Comparison on Two SGML Or XML DTD Files

The main purpose of a DTD file is to identify and classify the official building blocks of the XML document. It is commonly used to define the structure of the XML document by creating a list of the lawful elements. The declaration of the DTD can be done in two ways. The first one is to declare it inline in the XML document that you have created. The other way is to declare it as an external reference.


Before you learn how to make DTD comparison, you should know why you have to use this file format. XML provides the users with an application that makes them share data independently. If they use DTD, they are allowed to make use of a common DTD so that they can interchange the data. Here, you can utilize standard DTD so that you can verify the validity of the data that you have received. Another benefit from DTD is that you can employ this to make sure that your own data is legal.


With DTD known as the building blocks of XML, one can conclude that this is an important element in the documents. You can define the elements in the XML document by simply using DTD. Here, the DTD elements that you can create are empty elements along with elements with data, with children or sequences and wrapping. You can also declare one occurrence of the same element or a mixed content. DTD attributes on the other hand can be declared using the ATTLIST declaration. You can build a default attribute value, implied attribute, fixed attribute value or enumerated attribute values.


Now, if you have a problem with the DTD file format that you are working on, it can be caused by some registry failures. To solve this, simply scan windows registry in your computer so that you can repair the conflicts in the XML DTD files. Let us now proceed to DTD comparison. You can easily perform this by adding a new script to your XML document, which is "dtd-compare.py." This can compare the defined vocabularies in the DTD files. You can see here which among the elements are present or absent.


Comparing SGML or XML DTDs is more complicated. To make it simpler, you can use "dtddiff." This compares the two DTDs on XML files that are based upon the dumps produced by "dtdparse." Since the main dtddiff processes include the XML dumps, you do not have to perform a full reparse on the DTD files. What dtddiff does is to make a comparison based on the structure of the files. This means that you will not have to worry about the declaration order because it goes unaffected by this command.


DTD files formalize the markup languages and more importantly, it develops markup language generations by checking them. Nowadays, there are some who do not learn the arcane DTD syntax. They can simply create a script that depends on the existing libraries that parse the DTD files. Dealing with DTDs can be quite complicated but with further researching and educating, you will ultimately understand the deep DTD file format.



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